This invention relates to product cooling and more specifically to a method, system and apparatus for rapidly cooling fresh meat, pork, sheep products or the like to retard bacterial growth thereon while simultaneously minimizing dehydration thereof.
It has long been a problem in the art of processing meat, and the like to simultaneously cool such products at a rate sufficient to prevent the growth of bacteria and at the same time maintain the moisture content of the product at a high level. A high moisture content in such products not only adds greatly to the taste and appearance of such products but the overall weight of the product is greater resulting in a higher price realized when the product is sold by the pound. High moisture content must be achieved without any water contacting the product which would result in its condemnation by inspectors of the United States Department of Agriculture (USDA).
Typically, the carcass of the warm, freshly slaughtered animal is placed or hung in an enclosed room or holding chamber through which refrigerated air is circulated to thereby reduce as rapidly as possible the temperature of the carcass from approximately 100 degrees F. down to approximately 40 degrees F. to stop bacterial growth thereon. Prior art cooling systems are able to achieve this 60 degree F. temperature drop by slowly circulating cool air through the chamber containing the product and through a cooling unit such as a plate fin-type evaporator connected to a conventional refrigeration system. The air would have a relative humidity of approximately 60 percent. The temperature of this slow moving relatively dry air would increase 3 or 4 degrees F. as a result of the heat given off by the product. This 3 or 4 degrees F. temperature rise would then cause the air to have an affinity for moisture which it would take out of the product causing the product to shrink from dehydration. Air having such a 60 percent relative humidity slowly circulated over the product in prior art systems would typically result in shrinkage of the product from dehydration of approximately 0.75 percent if the product was beef and 1.5 percent if the product was pork.
In such prior art systems the air passing through the cooling unit was typically cooled to approximately 28 degrees F. and then circulated over the product where it picked 3 to 4 degrees F. and was then returned to the cooling unit with a temperature of approximately 32 degrees F. The air was passed through the cooling unit at approximately 500 feet per minute and the water was removed therefrom while keeping the relative humidity at approximately 60 percent as aforementioned. To reduce the temperature of the air in the plate fin-type evaporator this 3 or 4 degrees F. prior to its discharge back into the chamber required the refrigerant passing through the evaporator to be low or approximately 13 degrees F. and required approximately 1.2 horsepower per ton to thus cool the air. A higher velocity of air through the plate fin-type evaporator of the prior art was not achievable without an excessive amount of free water being entrained therein which would then settle on the product resulting in its condemnation as aforementioned.
Applicant discovered that if the velocity of the air being circulated over the product and through the cooling unit is very high, the air would pick up less heat, for example, only 1.5 to 2.0 degrees F., from heat given off by the product before the air is returned to the cooling unit. This low temperature increase is insufficient to cause the air to crave moisture thus less moisture is taken out of the product. In addition because of this low increase air temperature, the cooling unit requires less energy consumption to remove this heat from the air prior to its recirculation back to the chamber holding the product. Thus, the refrigerant passing through the evaporator cooling coils of the cooling unit can be at a higher temperature than that of the prior art, for example, approximately 28 degrees F. At this 28 degrees F. refrigerant temperature, the cooling coils of the evaporator run "wet", thus less moisture is removed from the air passing over them and applicant is able to maintain the relative humidity of the air circulating over the product at between 90 and 100 percent which further reduces absorption of moisuture from the product. Applicant's novel air diffuser design adjacent the cooling coils of the cooling unit insures that all free, entrained water is removed from the moisture ladened air so as not to fall on the surface of the product. Operation of applicant's system has resulted in dehydration or shrinkage of only 0.25 percent if the product were freshly slaughtered beef and 0.50 percent if the product were pork. As can readily be seen, this is only one-third of the shrinkage of the product experienced by the prior art methods.
This energy savings and reduction in the shrinkage of the product is achieved by applicant's use of a spiral wrap fin-type evaporator or cooling means in the refrigeration system which includes the air diffuser of applicant's novel design. The cooling system will be described in detail later. It is sufficient to say at this point, however, that applicant's diffuser design permits air to be forced past or over the cooling coils in the evaporator at a face velocity of between 800 and 1,000 feet per minute and exit with a very low free, entrained water content but with a relative humidity of between 90 and 100 percent as aforestated. Because the cooling coils of the evaporator are run "wet", that is, passing refrigerant through them having a temperature of approximately 28 degrees F., only 0.9 horsepower per ton to cool the air is required or a 0.3 horsepower per ton savings over the prior art systems. The air thus rapidly recirculated by applicant's system is only heated a maximum of 2 degrees F. before being returned to the evaporator for recooling contrasted with a prior art difference of 4 degrees F. as aforementioned.
Thus, applicant's novel cooling system to be hereinafter described in detail not only results in less weight loss or shrinkage due to dehydration of the product, it achieves this result consuming less power than the prior art cooling systems.
It is therefore the primary object of the present invention to provide a superior method and apparatus for minimizing dehydration of freshly slaughtered meat products and the like and do it with less electrical power consumption.
It is another object of the present invention to provide a method and apparatus for accomplishing the stated purpose which maintains a high degree of relative humidity in the cooled air but a low entrained or free water content.
It is yet another object of the present invention to provide a method and apparatus for accomplishing the stated purpose which has a cooling means that is capable of moving air through it at a very high face velocity and recirculating it rapidly over the meat product resulting in less heat and thus less moisture being given up by the product.
It is a further object of the present invention to provide an extremely efficient air cooling means having a novel air diffusing device incorporated therein.